You cannot use this function with a handle to a nonseeking device, such as a communications device.

Use this function to truncate or extend a file. If the file is extended, the contents of the file between the old EOF position and the new position are not defined. Call the SetFilePointer function to set the file pointer to the desired position before setting the end of the file.

If you called the CreateFileMapping function to create a file-mapping object for hFile, you must first call the UnmapViewOfFile funciton to unmap all views and call the CloseHandle function to close the file-mapping object before you call this function.